1. Field of the Invention
The present invention relates to an apparatus for and a method of measuring a workpiece on a machine tool, wherein the workpiece is measured with a wired or wireless measuring head attached to a movable unit moving relatively to the workpiece in a machining area of the machine tool.
2. Description of the Related Art
For a machine tool such as a machining center, there have been proposed techniques of measuring the shape of the surface of a workpiece attached to the machine tool without removing the workpiece from the machine tool after machining. For example, a workpiece inspection system for a machine tool is described in Japanese published patent application JP2007-518579 (corresponding to WO 2005/065884).
This work inspection system has a probe (corresponding to the measuring head of the present invention) mounted on a main spindle of the machine tool. The data measured, when a needle of the probe contacts the workpiece, is output and an NC (numerical control) device also acquires position data of the probe. The measurement data and the position data are combined to inspect the workpiece.
The inspection system described in JP2007-518579 is configured in such a manner that a programmable controller receives the position data of the probe from the NC device for calculating. Accordingly, modification or change of the NC device or the programmable controller such as adding a new function thereto has been required in order to inspect the workpiece.
In addition, the inspection system, which is subject to restrictions of the NC device and the programmable controller, is not necessarily applicable to all machine tools.
The operation of acquiring the position data of the probe from the NC device is performed intermittently during the operation control on the machine tool, which is the primary role of the NC device. As a result, it has been difficult to acquire the position data of the probe at a precise timing. In addition, it has been also impossible to shorten the time interval for acquiring the position data to acquire a large amount of measurement data from the probe at high speed. Therefore, it has been difficult to measure a wide range of workpieces in a short time.